Dentist charge for filling

My family and I have recently attended an appointment at a new NHS dental practice where I had the usual check up where they also took X rays. The cost was Band 1 £17.50.

Three weeks later I received a phone call asking me to attend another appointment as they think something was noticed after they examined my xrays. The dentist blew cold air onto my teeth and could find nothing wrong and I felt no pain or discomfort anywhere. However she noticed I required an existing filling which she said she could patch up with some filler or remove the whole filling and put a new one in but said whatever she did would then cost me £48. Band 2.

After doing some research online I looked on the nhs.choices website and in band 1 £17.50 covers "marginal correction of fillings" I phoned my dental surgery up and they just rhymed off what was on the nhs.uk poster so I phoned up my local pct trust and pow office and they were unaware of this line about marginal correction of fillings and they only told me what was on the nhs poster that is displayed on the reception desk.

Therefore I am now unsure and wonder if anyone can please tell me if the nhs.ukchoices website is correct with what they state under Band 1 charges as marginal correction of fillings and if my dentist should have spotted this at my 1st appointment under band 1. Anybodys advice would be appreciated.